Re: Safe vm.overcommit_ratio for Large Multi-Instance PostgreSQL Fleet

On 8/6/25 17:14, Frits Hoogland wrote:
>> As I said, do not disable swap. You don't need a huge amount, but
>> maybe 16 GB or so would do it.

> Joe, please, can you state a technical reason for saying this?
> All you are saying is ‘don’t do this’.
>
> I’ve stated my reasons for why this doesn’t make sense, and you don’t give any reason.

What do you call the below?

>> Op 6 aug 2025 om 18:33 heeft Joe Conway <mail(at)joeconway(dot)com> het volgende geschreven:

>> * Swap is what is used when anonymous memory must be reclaimed to
>> allow for an allocation of anonymous memory.
>>
>> * The Linux kernel will aggressively use all available memory for
>> file buffers, pushing usage against the limits.
>>
>> * Especially in the older 4 series kernels, file buffers often
>> cannot be reclaimed fast enough
>>
>> * With no swap and a large-ish anonymous memory request, it is
>> easy to push over the limit to cause the OOM killer to strike.
>>
>> * On the other hand, with swap enabled anon memory can be
>> reclaimed giving the kernel more time to deal with file buffer
>> reclamation.
>>
>> At least that is what I have observed.

If you don't think that is adequate technical reason, feel free to
ignore my advice.

--
Joe Conway
PostgreSQL Contributors Team
Amazon Web Services: https://aws.amazon.com